Substantially all tennis rackets in general use today have a plurality of characteristics which have proven to be positive in effect, other characteristics found to have a negative effect, and still other characteristics which are considered to be neutral in their effect.
Size -- Substantially all tennis rackets in practical use today employ a strung surface of approximately 70 square inches. In most cases, the head is elliptical with the strung surface having a longitudinal axis of approximately 101/2 inches and a minor axis of approximately 81/2 inches. This relatively small strung surface is believed to be disadvantageous from a playing standpoint, particularly in making no attempt to use the size and location of the strung surface to centralize the center of percussion of the racket and from several other standpoints as will be made clear hereinafter.
Center of percussion --to The designation "center of percussion", sometimes called the "sweet spot", is an important concept in tennis racket design. For the purposes of this disclosure, the "center of percussion" of the racket is the location at which an impacting ball results in zero kick or jar to the player's hand. A disadvantage of racket proposed heretofore and in common use today is that the center of percussion is close to the throat and is spaced from the intersection of the major and minor axes of the strung surface. For example, see U.S. Pat. 1,539,019 which suggests the use of weights added to an otherwise light racket to change the location of the center of percussion. A conventional racket having a center of percussion relatively close to the throat of the racket is undesirable from several viewpoints. The average player tends to strike a ball at the geometric center of the racket and hence at a location spaced from the center percussion.
Coefficient of restitution -- The coefficient of restitution is the ratio of the relative incoming velocity of the ball as struck by the racket as compared with its outgoing velocity after impact. Players perfer a racket designed such that their average strokes impact an area of maximum coefficient of restitution in order to obtain the greatest possible return velocity to their shots without having to swing the racket harder and thereby risking loss of control and accuracy.
Strength -- A disadvantage of most tennis rackets in general use today, whether made of wood or metal, is their tendency to break. The breakage most often occurs in the shaft of the racket just below the head or in the flare of the racket just above the throat.
Strings -- The only two materials in common use today for the stringing of tennis rackets are nylon and animal gut. Of the two materials, nylon has the advantage of being approximately one third the cost, of being weatherproof, and being two to three times more durable as compared with gut. On the other hand, gut is unmistakably the preferred material for use by players of medium-to-expert ability in the case of conventional rackets where the relatively short strings require a material of maximum elasticity and resilience. There has long been a great need for a racket which utilizes strings of nylon or other synthetic or composite materials but which produces substantially the same feel as animal gut when the racket is in use.